Natrix astreptophora algerica ( Hecht, 1930 )

Natrix astreptophora algerica ( Hecht, 1930) View in CoL (n=16)

Hecht (1930) described the taxon Tropidonotus natrix algericus based on two specimens from Algeria, one each from “Südalgier” (ZMB 19636, holotype) and “ Algier ” (ZMB 1935, paratype). Both are ethanol-preserved specimens in the collection of the Museum of Naturkunde, Berlin, and were examined by us. Fritz & Schmidtler (2020) concluded that the type locality “Südalgier” (southern Algeria) must be corrected to an unidentified site in northern Algeria. In addition, they proposed to recognize Algerian and Tunisian populations, representing a unique genetic lineage of N. astreptophora , under the name Natrix astreptophora algerica ( Hecht, 1930) as a distinct subspecies. We concur with this suggestion.

Grass snakes are only known from a few precise localities in the north of Algeria and Tunisia ( Gervais 1848; Strauch 1862; Lallement 1866; Boulenger 1891; Olivier 1894; Doumergue 1901; Gadeau de Kerville 1908; Schleich et al. 1996; Brito et al. 2008; Escoriza & Ben Hassine 2017; Rouag et al. 2024; R. Ouni pers. comm.; Appendix 2). One of them, “Tifret” (F. Lataste in Boulenger 1891), was traditionally identified with a village in northwestern Algeria called Tifrit, representing the only record in that part of the country ( Sindaco et al. 2013; Trape 2023). However, according to the trips made by Lataste in Algeria, the correct locality should be Tifrit N’Aït el Hadj (P.- A. Crochet and M. Beddek pers. comm.), a site within the known distribution range of N. astreptophora . Thus, the actual distribution gap between the two North African lineages ( Morocco and Algeria-Tunisia) is more than 650 km wide. Another putative locality, Gafsa, central Tunisia, with a physical voucher specimen in the collection of the Muséum national d’Histoire naturelle, Paris (MNHN-RA-1983.507, not studied by us, Appendix 2), is highly questionable because Gafsa is an oasis situated in desert climate.

Sochurek (1979) proposed that the subspecies “ Natrix natrix algirus ” [sic] is valid, but believed it is distributed from the Middle Atlas to northwestern Tunisia, while he tentatively assigned the grass snakes from the Rif Mountains to “ N. n. astreptophora ”. Sochurek (1979) characterized “ N. n. algirus ” by its closed light collar – this is a trait not present in grass snakes from Algeria and Tunisia. According to Sochurek (1979), the collar is still present in adults and is posteriorly bordered by longer dark nuchal markings compared to “ N. n. astreptophora ”; moreover, the body of “ N. n. algirus ” has frequently small dark spots. When it is considered that European N. a. astreptophora can become plain-colored early in ontogeny, this characterization is mostly correct. However, among 16 grass snakes from Algeria and Tunisia examined for the present study, there are also three large and aged specimens from Algeria (1) and Tunisia (2) without or with very faint collars, two of them with completely or nearly unicolored body (see Fig. 6C, D View FIGURE 6 ). The third specimen (BEV.8874) consists of the head only. The TL of the figured specimen from Algeria ( Fig. 6D View FIGURE 6 ), most likely a female, exceeds 100 cm. Moreover, according to our data, the light collar of N. a. algerica is always interrupted by a narrow dark sagittal line, while Moroccan grass snakes have closed collars. This supports that Sochurek (1979) lumped the two North African lineages together, as is also evident from the distribution range assigned.

Actually, in all hatchlings, juveniles, and young adults from Algeria (n=5) and Tunisia (n=8) that we examined, the light neck collar is interrupted by a narrow black line (at least one scale wide). In contrast, all 11 individuals from Morocco in which the collar is visible have it continuous and closed. An interrupted collar may also occur in European grass snakes ( Fig. 7 View FIGURE 7 ). Elsewise, the head coloration of hatchlings and small juveniles of N. a. algerica resembled that of Moroccan populations. Hatchlings and small juveniles of the two North African lineages share a white-yellowish color of the collar that extends to the three postoculars, the preocular scales, and the first supralabial scales (with black lines separating the supralabial scales). The last supralabial scale has the same color as the collar, whereas the loreal scale is completely –or almost completely– black.

Hatchlings and small juveniles from Algeria and Tunisia have a brownish to greyish primary body color with or without small to medium-sized dorsal and lateral dark markings; if present, these are often less contrasting than in N. a. astreptophora and Moroccan grass snakes. Moreover, the shape of the dorsal markings can be different. Moroccan snakes tend to have a solid dark marking, while the dark markings may be divided in the Algerian-Tunisian specimens. Moreover, Algerian and Tunisian grass snakes seem to lose their hatchling spots very early and then become plain colored.

Based mainly on European material, Pokrant et al. (2016) supported their elevation of N. astreptophora as a distinct species by the lower number of ventral scales compared to other grass snake species (156–166 versus 162– 182). However, Hecht (1930) reported for the two types of Tropidonotus natrix algericus 163 and 171 ventral scales, respectively, suggesting that N. a. algerica might have a higher number of ventrals than European conspecifics. A Tunisian specimen in the collection of the Zoologisches Forschungsmuseum A. Koenig, used by Pokrant et al. (2016) and studied by us, has 163 ventrals (ZFMK 67196); two live snakes from Tunisia measured in May 2025 had 162 and 163 ventrals. In addition, the long tail of N. n. algerica is remarkable, representing 22.0–28.5% of the TL in the three studied complete museum specimens and the two Tunisian live snakes, corresponding to the longest tails known in N. astreptophora .